Control of an environment in the processing of semiconductors is very important. Typically, semiconductors are fabricated from wafers within a processing chamber. One or more diffusion steps may be followed (or preceded) by masking steps to define semiconductor fabrication sites on a wafer. Once fabrication sites have been defined, the process may be repeated any number of times depending upon the complexity of the fabricated device.
Once semiconductor devices have been created at the defined sites, a set of connections may be formed at the defined sites. Connections may be formed by any number of masking, deposition and etching steps.
At each step of the fabrication process, different reactive materials may be used. Usually the reactive materials are in the form of gases.
In order to provide a consistent semiconductor product, the diffusion, deposition and etching processes must be reliably controlled usually through the precise control of the reactive gases. Typically, this is accomplished by controlling the flow of the reactive materials into the processing chamber.
In semiconductor thin film processing, it is very important to know the precise gas composition within the processing chamber. Conventionally, this is accomplished primarily by flow controls, but flow control alone does not identify the proportions of reactant gas present within the processing chamber especially when there are other gases present, such as carrier gases or background gases. Accordingly, a need exits for a better method of measuring gas content, especially in a process environment involving a multitude of gases.